# Life expectancy: source and method

## Citation

Riley (2005); Zijdeman et al. (2015); HMD (2025); UN WPP (2024) – with major processing by Our World in Data. “Life expectancy – Riley; Zijdeman et al.; HMD; UN WPP – Long-run data” \[dataset\]. Human Mortality Database, “Human Mortality Database”; United Nations, “World Population Prospects”; United Nations, “World Population Prospects – Interim Update”; Zijdeman et al., “Life Expectancy at birth v2”; James C. Riley, “Estimates of Regional and Global Life Expectancy, 1800–2001” \[original data\].

## What it measures

Period life expectancy is the number of years the average person born in a certain year would live if they experienced the same chances of dying at each age as people did that year. Unit: years.

## How the data were processed

This chart combines data from several sources. For country-level data before 1950, we use the Human Mortality Database (2025) data and Zijdeman et al. (2015). For country-years where these sources overlap, we use the Human Mortality Database.

For regional data, before 1950, we use Riley's (2005) estimates.

From 1950 onwards, we use the United Nations World Population Prospects (2024) for both country-level and regional data.

Detailed information on the source of each data point can be found on [this page](https://docs.google.com/spreadsheets/d/1LnrU1V3p2wq7sAPY4AHRdH1urol3cKev7prEvlLfSU4/edit?gid=0#gid=0).

## Where it was taken from

- Chart: [https://ourworldindata.org/grapher/life-expectancy](https://ourworldindata.org/grapher/life-expectancy)
- Full metadata: [https://api.ourworldindata.org/v1/indicators/1118466.metadata.json](https://api.ourworldindata.org/v1/indicators/1118466.metadata.json)
- Last updated by Our World in Data: 2025-10-22. Taken for this site on 22 October 2026.

Our World in Data publishes its data under the Creative Commons BY 4.0 licence; data produced by third parties keep their own licence, given in the full metadata. [How this site takes its figures](/method) · [All life expectancy figures](/life-expectancy).

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